The present invention relates to a rolling guide unit of rolling contact type linear or curved, such as circular, guide passage, particularly capable of being excellent in misalignment adjustment performance.
As a known example of such rolling guide unit, there is provided an example shown in FIG. 22 in which a rolling guide unit 100 is disposed so as to guide a table 102 with respect to a fixed base 101.
The rolling guide unit 100 is assembled in a manner that a movable member 104 having a U-shape in cross section is provided with a pair of upper and lower support portions 103 extending in a lateral direction, i.e. longitudinal direction of the movable member, and upper and lower surfaces of a guide rail disposed in the U-shaped hollow portion of the movable member 104 are supported by the support portions through upper and lower two rows of balls 106. In general, high rigidity is required for such rolling guide unit, and in the known art, the rigidity in every direction including vertical and horizontal directions is made high by applying a preload to the balls 106 and forming projecting ribs 107 to the upper and lower side surfaces of the guide rail 105 so as to project therefrom thereby to clamp the ribs 107 by the respective two rows of the balls 106 from the upper and lower directions thereof. Particularly, in the illustrated example, in order to equally support the load in the every direction, a contact angle .alpha. of a line X connecting contacting points of the ball 106 to two ball rolling grooves with respect to a virtual horizontal line is set to 45.degree..
The known rolling guide unit of the type shown in FIG. 22, however, has high rigidity, and accordingly, when a working error, for example, an angular error .theta. and a dimensional error .DELTA. in the horizontal direction, is caused to a mounting surface of the movable member 104, a misalignment is caused between the guide rail 105 and the movable member 104 at the time of clamping and fixing the rolling guide unit between the table 102 and the fixed base 101. Such misalignment constitutes a cause of an application of excessive force to the movable member 104, resulting in the increasing of a sliding resistance and abrasion of the balls 106 and the ball rolling groves, thus providing a problem.
Such misalignment will be avoided by increasing the working performance of the respective members of the rolling guide unit. However, the increasing of the working performance has a limit itself and involves cost increasing.
In the meantime, the misalignment will be somewhat reduced by making small the preload to be applied to the balls 106, but the high rigidity of the rolling guide unit will be reduced by making small the preload to be applied. As mentioned above, the requirement of the high supporting rigidity is contrary to the reduction of the misalignment of the members, and hence, in the prior art construction, it is difficult to satisfy both the requirements for the realization of the high rigidity and the less misalignment.